Robust insulated fuel injector for a gas turbine engine

ABSTRACT

A fuel injector for a combustor of a gas turbine engine is disclosed. The fuel injector includes a flange, a fitting boss, a stem, a gas fuel passage, a gas fuel fitting, and a gas heat shield. The fitting boss protrudes from the flange. The stem extends from the flange. The gas fuel passage extends through the stem. The gas fuel fitting is joined to the fitting boss. The gas heat shield extends from the gas fuel fitting at least partially through the gas fuel passage. The gas heat shield is sized to form a gas heat shield gap between the gas heat shield and the stem at the gas fuel passage.

TECHNICAL FIELD

The present disclosure generally pertains to gas turbine engines, and is directed toward an insulated fuel injector for a combustor of a gas turbine engine.

BACKGROUND

Gas turbine engines include compressor, combustor, and turbine sections. Fuel passing through the stem of fuel injectors in the combustor may cause temperature gradients in the stem, which may result in deflection of the stem.

U.S. Pat. No. 6,182,437 to L. Prociw discloses a method of pre-treating the fuel injectors to form a precipitant, such as coke, within the insulating air gap in a controlled and predictable manner prior to installation of the injector into the engine. The method involves filling an annular portion of the gap with a selected fluid, such as hydrocarbon fuel for example, and then curing the liquid to form a precipitant, such as coke, that remains physically and chemically stable at temperatures within the temperature operating range of the injector stem that permits relative thermally induced movement between the heat shield and the fuel passage.

The present disclosure is directed toward overcoming one or more of the problems discovered by the inventors or that is known in the art.

SUMMARY OF THE DISCLOSURE

A fuel injector for a combustor of a gas turbine engine is disclosed. In some embodiments, the fuel injector includes a flange, a fitting boss, a stem, a gallery portion, a gas fuel passage, a gas fuel fitting, a gas heat shield, and a barrel assembly. The flange includes mounting holes. The fitting boss protrudes from the flange. The stem extends from the flange in a direction opposite the fitting boss. The gallery portion is at an end of the stem distal to the flange. The gas fuel passage extends from the fitting boss to the gallery portion through the stem. The gas fuel fitting is joined to the fitting boss at the gas fuel passage. The gas heat shield extends from the gas fuel fitting at least partially through the gas fuel passage. The gas heat shield is sized to form a gas heat shield gap between the gas heat shield and the stem at the gas fuel passage. The barrel assembly is joined to the gallery portion.

In some embodiments, the fuel injector includes a flange, a fitting boss, a stem, a gallery portion, a liquid fuel passage, cap, a liquid heat shield, and a barrel assembly. The flange includes mounting holes. The fitting boss protrudes from the flange. The stem extends from the flange in a direction opposite the fitting boss. The gallery portion is at an end of the stem distal to the flange. The liquid fuel passage extends from the fitting boss to the gallery portion through the stem. The cap is joined to the fitting boss at the liquid fuel passage. The liquid heat shield extends from the cap towards the gallery portion within the liquid fuel passage. The liquid heat shield is sized to form a liquid heat shield gap between the liquid heat shield and the stem at the liquid fuel passage. The barrel assembly is joined to the gallery portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary gas turbine engine.

FIG. 2 is a perspective view of a fuel injector for the combustor of FIG. 1.

FIG. 3 is a cross-section of a portion of the fuel injector of FIG. 2.

FIG. 4 is a detailed view of a portion of the fuel injector cross-section of FIG. 3.

DETAILED DESCRIPTION

The systems and methods disclosed herein include a fuel injector with a fuel passage extending non-symmetrically through a stem of the fuel injector. In embodiments, a heat shield extends within the non-symmetrically located fuel passage. The heat shield may prevent heat from transferring between the stem and the fuel in the fuel passage. Preventing heat from transferring may prevent or reduce the formation of temperature gradients within the stem, which may lead to deflection of the fuel injector. Preventing heat from transferring may also prevent the liquid fuel from pyrolyzing.

FIG. 1 is a schematic illustration of an exemplary gas turbine engine 100. Some of the surfaces may have been left out or exaggerated (here and in other figures) for clarity and ease of explanation. Also, the disclosure may reference a forward and an aft direction. Generally, all references to “forward” and “aft” are associated with the flow direction of primary air (i.e., air used in the combustion process), unless specified otherwise. For example, forward is “upstream” relative to primary air flow, and aft is “downstream” relative to primary air flow.

In addition, the disclosure may generally reference a center axis 95 of rotation of the gas turbine engine, which may be generally defined by the longitudinal axis of its shaft 120 (supported by a plurality of bearing assemblies 150). The center axis 95 may be common to or shared with various other engine concentric components. All references to radial, axial, and circumferential directions and measures refer to center axis 95, unless specified otherwise, and terms such as “inner” and “outer” generally indicate a lesser or greater radial distance from center axis 95, wherein a radial 96 may be in any direction perpendicular and radiating outward from center axis 95.

A gas turbine engine 100 includes an inlet 110, a shaft 120, a compressor 200, a combustor 300, a turbine 400, an exhaust 500, and a power output coupling 600. The gas turbine engine 100 may have a single shaft or a dual shaft configuration.

The compressor 200 includes a compressor rotor assembly 210, compressor stationary vanes (stators) 250, and inlet guide vanes 255. The compressor rotor assembly 210 mechanically couples to shaft 120. As illustrated, the compressor rotor assembly 210 is an axial flow rotor assembly. The compressor rotor assembly 210 includes one or more compressor disk assemblies 220. Each compressor disk assembly 220 includes a compressor rotor disk that is circumferentially populated with compressor rotor blades. Stators 250 axially follow each of the compressor disk assemblies 220. Each compressor disk assembly 220 paired with the adjacent stators 250 that follow the compressor disk assembly 220 is considered a compressor stage. Compressor 200 includes multiple compressor stages. Inlet guide vanes 255 axially precede the compressor stages.

The combustor 300 includes one or more combustion chambers 305, one or more fuel injectors 310, and a combustor case 301 located radially outward from the combustion chamber 305. The combustion chamber 305 may include a grommet 306 for each fuel injector 310. Each fuel injector 310 may connect to combustion chamber 305 at a grommet 306. Each fuel injector 310 includes a barrel assembly 330 adjacent a combustion chamber 305, a flange 312 adjacent the combustor case 301, a fitting boss 315 protruding from the flange 312, and a stem 320 extending from the flange 312 in the direction opposite fitting boss 315, between the fitting boss 315 and the barrel assembly 330. The barrel assembly 330 may mate with the grommet 306.

The turbine 400 includes a turbine rotor assembly 410 and turbine nozzles 450. The turbine rotor assembly 410 mechanically couples to the shaft 120. As illustrated, the turbine rotor assembly 410 is an axial flow rotor assembly. The turbine rotor assembly 410 includes one or more turbine disk assemblies 420. Each turbine disk assembly 420 includes a turbine disk that is circumferentially populated with turbine blades. Turbine nozzles 450 axially precede each of the turbine disk assemblies 420. Each turbine disk assembly 420 paired with the adjacent turbine nozzles 450 that precede the turbine disk assembly 420 is considered a turbine stage. Turbine 400 includes multiple turbine stages.

The exhaust 500 includes an exhaust diffuser 510 and an exhaust collector 520. The power output coupling 600 may be located at an end of shaft 120. In the embodiment illustrated, power output coupling 600 is located at an aft end of shaft 120.

FIG. 2 is a perspective view of a fuel injector 310 for the combustor 300 of FIG. 1. Referring to FIG. 2, fitting boss 315, flange 312, and stem 320 may be an integral piece. Fitting boss 315 may include a cylindrical or prism shape extending from flange 312. Multiple fittings may be coupled to fitting boss 315. Liquid fuel, gas fuel, and air supply lines may be coupled to the fittings to supply liquid fuel, gas fuel, and air to the fuel injector 310. In the embodiment illustrated in FIG. 2, a liquid fuel fitting 316 is coupled to the side of fitting boss 315 and a gas fuel fitting 317 is coupled to the top surface of fitting boss 315. In the embodiment shown, fittings 318 and 319 are also coupled to the side of fitting boss 315. Fittings 318 and 319 may be used for liquid or gas pilot fuel supply or may be used to supply air.

Flange 312 may include a circular or polygonal shape. In the embodiment shown in FIG. 2, flange 312 includes a rectangular shape. Flange 312 includes multiple mounting holes 313. Mounting holes 313 may be used to affix fuel injector 310 to combustor case 301.

FIG. 3 is a cross-section of the fuel injector 310 of FIG. 2. Referring to FIGS. 2 and 3, fuel injector 310 may include a gallery portion 325. Gallery portion 325 may be the shape of a hollow cylinder and may be located at an end of stem 320, opposite and distal to flange 312. Gallery portion 325 may be an integral piece and may be machined or molded with fitting boss 315, flange 312, and stem 320.

Fuel injector 310 includes multiple passages extending from fitting boss 315, through stem 320, and to gallery portion 325. Each passage may be machined or drilled from the top of fitting boss 315, through stem 320, and to the gallery portion 325. A fitting, such as gas fuel fitting 317 or a cap 323 may be placed or inserted at the end of each passage at fitting boss 315. Gas fuel fitting 317 and cap 323 may each be joined to fitting boss 315 by a metallurgical bond, such as a weld or braze. As illustrated in FIG. 3, fuel injector 310 includes a liquid fuel passage 321 and a gas fuel passage 322. Liquid fuel passage 321 extends from fitting boss 315 to gallery portion 325. In the embodiment illustrated, liquid fuel passage 321 extends completely through fitting boss 315 with a cap 323 inserted in the end of liquid fuel passage 321 at fitting boss 315. Liquid fuel passage 321 may be in the shape of a cylinder, such as a right circular cylinder.

Gas fuel passage 322 extends from fitting boss 315 to gallery portion 325. In the embodiment illustrated, gas fuel passage 322 extends completely through fitting boss 315 with a gas fuel fitting 317 inserted in the end of gas fuel passage 322 and joined to fitting boss 315 at gas fuel passage 322. Gas fuel passage 322 may be in the shape of a horizontal cylindrical segment. The edges between the cylindrical portion and the planar portion that make up the cylindrical segment may each have an edge break, such as a fillet or a chamfer. These passages may supply liquid and gas pilot fuel or air to the barrel assembly 330.

Fuel injector 310 may include an assembly feature 328. Assembly feature 328 may be an indent or concavity in the hollow cylinder shape of stem 320 which can aid in assembly of the gas turbine engine. Assembly feature 328 may protrude into gas fuel passage 322 and may be proximal gallery portion 325.

Fuel injector 310 may include a liquid heat shield 360 and a gas heat shield 380. Liquid heat shield 360 extends within liquid fuel passage 321. Liquid heat shield 360 may extend from cap 323 towards gallery portion 325. Liquid heat shield 360 may be the shape of a hollow cylinder. Liquid heat shield 360 may include a first liquid heat shield end 361 and a second liquid heat shield end 362. First liquid heat shield end 361 may be joined to the cap 323 that is used to cap liquid fuel passage 321 at fitting boss 315. First liquid heat shield end 361 may be joined to the cap 323 by a metallurgical bond, such as a weld or braze.

Second liquid heat shield end 362 may be located adjacent gallery portion 325. In some embodiments, second liquid heat shield end 362 is sealed to stem 320 at liquid fuel passage 321. In other embodiments, second liquid heat shield end 362 is sealed to gallery portion 325. In yet other embodiments, second liquid heat shield end 362 includes a standoff extending radially outward and contacting liquid fuel passage 321. In embodiments where first liquid heat shield end 361 and second liquid heat shield end 362 are both affixed or sealed to other components, liquid heat shield 360 may include and expansion feature, such as a bellows to allow for differential thermal expansion between the liquid heat shield 360 and the stem 320.

Liquid heat shield 360 may be in fluid communication with liquid fuel fitting 316 and barrel assembly 330 so that liquid fuel will pass through liquid heat shield 360 when traveling from liquid fuel fitting 316 to liquid gallery 337 within barrel assembly 330.

Liquid heat shield 360 may be sized so that there is a Liquid heat shield gap 369 between liquid heat shield 360 and stem 320 at liquid fuel passage 321. In the embodiment illustrated, liquid heat shield gap 369 is an annular shape, such as a hollow cylinder. In other embodiments, liquid heat shield gap 369 may include other shapes due to the design of fuel injector 310. Liquid heat shield gap 369 may not be in fluid communication with liquid heat shield 360, liquid gallery 337, and liquid fuel fitting 316.

Gas heat shield 380 extends within gas fuel passage 322. Gas heat shield 380 may extend from gas fuel fitting 317 towards gallery portion 325. Gas heat shield 380 may be the shape of a hollow horizontal cylindrical segment. The edges of the hollow horizontal cylindrical segment shape may be rounded. Gas heat shield 380 may include a first gas heat shield end 381 and a second gas heat shield end 382. First gas heat shield end 381 may be joined to gas fuel fitting 317 by a metallurgical bond, such as a weld or braze. Second gas heat shield end 382 is distal to the gas fuel fitting 317 and may be located within gas fuel passage 322. In embodiments, second gas heat shield end 382 is proximal gallery portion 325. In the embodiment illustrated, second gas heat shield end 382 is adjacent assembly feature 328. In some embodiments, second gas heat shield end 382 is sealed to stem 320 at gas fuel passage 322. In other embodiments, second gas heat shield end 382 includes a standoff extending outward and contacting gas fuel passage 322. In embodiments where first gas heat shield end 381 and second gas heat shield end 382 are both affixed or sealed to other components, gas heat shield 380 may include and expansion feature, such as a bellows to allow for differential thermal expansion between the gas heat shield 380 and the stem 320.

Gas heat shield 380 may be in fluid communication with gas fuel fitting 317 and barrel assembly 330 so that gas fuel will pass through gas heat shield 380 when traveling from gas fuel fitting 317 to gas gallery 327 within barrel assembly 330.

Gas heat shield 380 may be sized so that there is a gas heat shield gap 389 between gas heat shield 380 and stem 320 at gas fuel passage 322. Gas heat shield gap 389 may have a hollow horizontal cylindrical segment shape. Gas heat shield gap 389 may not be in fluid communication with gas heat shield 380, gas gallery 327, and gas fuel fitting 317.

Gas heat shield 380 extends at least partially through gas fuel passage 322. In some embodiments, the length of gas heat shield 380 is from 60 to 100 percent of the length of gas fuel passage 322. In other embodiments, gas heat shield 380 is from 65 to 85 percent of the length of gas fuel passage 322. In yet other embodiments, gas heat shield 380 is from 70 to 80 percent of the length of gas fuel passage 322. In yet further embodiments, gas heat shield 380 is from 75 to 78 percent of the length of gas fuel passage 322.

Fuel injector 310 may also include a stem heat shield 324. Stem heat shield 324 may be in the shape of a hollow cylinder and may include at stem heat shield support flange 329 extending radially inward from the hollow cylinder shape at each end of the stem heat shield 324 adjacent the flange 312 and the gallery portion 325. The stem heat shield support flanges 329 may act as a stand-off or spacer forming an insulating gap 339, an annular space between stem 320 and stem heat shield 324.

Referring to FIG. 3, barrel assembly 330 and gallery portion 325 may share a common axis 331. All references to radial, axial, and circumferential directions and measures relating to barrel assembly 330 and gallery portion 325 refer to axis 331 and terms such as “inner” and “outer” generally indicate a lesser or greater radial distance from axis 331. Gallery portion 325 may revolve about axis 331.

Barrel assembly 330 may include swirler assembly 350, gas inner tube 340, liquid tube 370, inlet swirler 379, and heat shield 390. Swirler assembly 350 may be a single integral piece or may be multiple pieces metallurgically bonded together, such as by brazing or welding. Swirler assembly 350 may include gas outer tube 351 and outlet swirler 355. Gas outer tube 351 may extend from gallery portion 325. Gas outer tube 351 and gallery portion 325 may be metallurgically bonded, such as brazed or welded. Gas outer tube 351 may include tapered region 352 and cylindrical region 353, and injector cap 354. Tapered region 352 may extend axially from gallery portion 325.

Tapered region 352 may taper from a larger diameter to a smaller diameter adjacent cylindrical region 353. Tapered region 352 may include the shape of a funnel or a frustum of a hollow cone. The smaller diameter of tapered region 352 may match the diameter of cylindrical region 353. Barrel assembly 330 may be joined to stem 320 at gallery portion 325 by a metallurgical bond, such as a weld or braze. In some embodiments, tapered region 352 is metallurgically bonded to gallery portion 325. In the embodiment illustrated, tapered region 352 includes a lip sized to fit into and mate with an end of gallery portion 325.

Cylindrical region 353 extends axially from tapered region 352 in the direction opposite gallery portion 325. Cylindrical region 353 may include a constant diameter and may be the shape of a hollow right circular cylinder. Injector cap 354 may be located at the end of gas outer tube 351, such as at the end of cylindrical region 353 opposite and distal to tapered region 352, and may be located distal to gallery portion 325. Injector cap 354 may extend radially inward from the end of the cylindrical region 353 distal to tapered region 352.

Outlet swirler 355 may be adjacent injector cap 354. Outlet swirler 355 may have swirler vanes 356 configured to swirl the fuel air mixture exiting the fuel injector 310 and may be configured to circumferentially deflect compressor discharge air.

Gas inner tube 340 includes intermediate gallery portion 341, transition portion 342, and gas inner cylindrical portion 343. Intermediate gallery portion 341, transition portion 342, and gas inner cylindrical portion 343 may each be coaxial. Intermediate gallery portion 341 may be located within gallery portion 325 and may be located radially inward from gallery portion 325. Intermediate gallery portion 341 may generally have a hollow cylinder shape.

Intermediate gallery portion 341 may also include a liquid fuel inlet 344. Liquid fuel inlet 344 aligns with and is in fluid communication with liquid fuel passage 321. Liquid fuel inlet 344 may extend through the hollow cylinder shape of intermediate gallery portion 341 Intermediate gallery portion 341 may interface with and may form a seal with stem 320 at the communication point of liquid fuel inlet 344 and liquid fuel passage 321.

Transition portion 342 extends from intermediate gallery portion 341 and is located between intermediate gallery portion 341 and gas inner cylindrical portion 343 within gallery portion 325. Transition portion 342 may extend in the axial direction and may be located radially inward from gallery portion 325. Transition portion 342 is configured to reduce the diameter of gas inner tube 340 from intermediate gallery portion 341 and gas inner cylindrical portion 343. Transition portion 342 may include the shape of a funnel, such as the frustum of a hollow cone (a hollow frustoconical shape) with the larger diameter located at the intermediate gallery portion 341 and the smaller diameter located at the gas inner cylindrical portion 343. Transition portion 342 and gallery portion 325 may be configured to form a gas gallery 327 adjacent and in fluid communication with gas fuel passage 322.

Gas inner cylindrical portion 343 extends from the end of transition portion 342 with the smaller diameter, distal to where intermediate gallery portion 341 extends from transition portion 342. Gas inner cylindrical portion 343 may extend in the axial direction. Gas inner cylindrical portion 343 includes a hollow cylinder shape and extends through gas outer tube 351 to injector cap 354 forming a gas fuel annulus 335 there between. Gas inner cylindrical portion 343 may be located radially inward from gas outer tube 351.

Liquid tube 370 may be located within gas inner tube 340 and may be located radially inward from gas inner tube 340. Liquid tube 370 includes inner gallery portion 371, inner transition portion 372, and liquid inner cylindrical portion 373. Inner gallery portion 371, inner transition portion 372, and liquid inner cylindrical portion 373 may be coaxial. Inner gallery portion 371 may be located within intermediate gallery portion 341 and may be radially inward from intermediate gallery portion 341. Inner gallery portion 371 and intermediate gallery portion 341 may form liquid gallery 337 there between. The liquid gallery 337 being in flow communication with liquid fuel inlet 344 and the liquid fuel passage 321. Inner gallery portion 371 may contact and interface with the end of intermediate gallery portion 341 distal to transition portion 342 to form a seal. Inner gallery portion 371 may also be configured to interface with inlet swirler 379.

Inner transition portion 372 may generally have a frustoconical shape with a bore extending there through. Inner transition portion 372 may extend from inner gallery portion 371 and may be located axially between inner gallery portion 371 and liquid inner cylindrical portion 373. The outer diameter of inner transition portion 372 reduces from inner gallery portion 371 to liquid inner cylindrical portion 373.

Liquid inner cylindrical portion 373 may extend from inner transition portion 372 and may extend in the axial direction. Liquid inner cylindrical portion 373 may extend within gas inner cylindrical portion 343 forming a liquid fuel annulus 336 there between and may be located radially inward from gas inner cylindrical portion 343. The liquid fuel annulus 336 may be in fluid communication with liquid gallery 337. Inner gallery portion 371, inner transition portion 372, and liquid inner cylindrical portion 373 form air cavity 338 extending through liquid tube 370.

Inlet swirler 379 may is configured to swirl and direct compressor discharge air into the fuel injector 310. Inlet swirler 379 may be inserted into the end of the hollow cylinder shape of gallery portion 325. Inlet swirler 379 may also be configured to partially insert into inner gallery portion 371.

Heat shield 390 includes a bell mouth portion 391 and a shield cylindrical portion 392. Bell mouth portion 391 may include the shape of a funnel, such as a hyperbolic funnel, bell, or segment or frustum of a pseudosphere. Bell mouth portion 391 is configured to be inserted and fit within inlet swirler 379.

Shield cylindrical portion 392 may extend from bell mouth portion 391 and within liquid inner cylindrical portion 373. Shield cylindrical portion 392 may be located radially inward from liquid inner cylindrical portion 373 forming an insulating gap 339 there between. Insulating gap 339 may be an annular space between heat shield 390 and liquid tube 370.

Heat shield 390 may include a thickened portion 393. The thickened portion 393 may be located on shield cylindrical portion 392 adjacent bell mouth portion 391.

FIG. 4 is a detailed view of a portion of the fuel injector 310 cross-section of FIG. 3. As illustrated in FIG. 4, gas fuel fitting 317 may include a gas fuel fitting body 311 and a gas fuel fitting transition portion 314. Gas fuel fitting body 311 may generally be a solid of revolution forming a fitting bore 309 there in. Fitting bore 309 may generally be in the shape of a cylinder. Gas fuel fitting transition portion 314 is configured to adjust the required flow area for the gas fuel passage 322 and may be configured to transition from the cylindrical shape of fitting bore 309 to the horizontal cylindrical segment shape of the gas fuel passage 322. In the embodiment illustrated, gas heat shield 380 connects to gas fuel fitting transition portion 314. In other embodiments, gas heat shield 380 connects to gas fuel fitting body 311.

Liquid heat shield gap 369 may have a liquid heat shield gap distance 368. Liquid heat shield gap distance 368 may generally be the clearance distance, such as the radial distance, between the outer surface of liquid heat shield 360 and the surface of liquid fuel passage 321. Liquid heat shield gap 369 may be sized to prevent the liquid fuel within liquid heat shield 360 from cooling stem 320 around liquid fuel passage 321. In some embodiments, liquid heat shield gap distance 368 is from 5 mils to 15 mils. In other embodiments, liquid heat shield gap distance 368 is within a predetermined tolerance of 10 mils, such as plus or minus 1 mil, 2 mils, or 3 mils.

Gas heat shield gap 389 may have a gas heat shield gap distance 388. Gas heat shield gap distance 388 may generally be the clearance distance between the outer surface of gas heat shield 380 and the surface of gas fuel passage 322. Gas heat shield gap 389 may be sized to prevent the gas fuel within gas heat shield 380 from cooling stem 320 gas fuel passage 322. In some embodiments, gas heat shield gap distance 388 is from 5 mils to 15 mils. In other embodiments, gas heat shield gap distance 388 is within a predetermined tolerance of 10 mils, such as plus or minus 1 mil, 2 mils, or 3 mils.

One or more of the above components (or their subcomponents) may be made from stainless steel and/or durable, high temperature materials known as “superalloys”. A superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys may include materials such as HASTELLOY, alloy x, INCONEL, WASPALOY, RENE alloys, HAYNES alloys, alloy 188, alloy 230, INCOLOY, MP98T, TMS alloys, and CMSX single crystal alloys.

INDUSTRIAL APPLICABILITY

Gas turbine engines may be suited for any number of industrial applications such as various aspects of the oil and gas industry (including transmission, gathering, storage, withdrawal, and lifting of oil and natural gas), the power generation industry, cogeneration, aerospace, and other transportation industries.

Referring to FIG. 1, a gas (typically air 10) enters the inlet 110 as a “working fluid”, and is compressed by the compressor 200. In the compressor 200, the working fluid is compressed in an annular flow path 115 by the series of compressor disk assemblies 220. In particular, the air 10 is compressed in numbered “stages”, the stages being associated with each compressor disk assembly 220. For example, “4th stage air” may be associated with the 4th compressor disk assembly 220 in the downstream or “aft” direction, going from the inlet 110 towards the exhaust 500). Likewise, each turbine disk assembly 420 may be associated with a numbered stage.

Once compressed air 10 leaves the compressor 200, it enters the combustor 300, where it is diffused and fuel is added. Air 10 and fuel are injected into the combustion chamber 305 via fuel injector 310 and combusted. Energy is extracted from the combustion reaction via the turbine 400 by each stage of the series of turbine disk assemblies 420. Exhaust gas 90 may then be diffused in exhaust diffuser 510, collected and redirected. Exhaust gas 90 exits the system via an exhaust collector 520 and may be further processed (e.g., to reduce harmful emissions, and/or to recover heat from the exhaust gas 90).

Gas turbine engine 100 may be configured to operate on multiple types of fuels. Referring to FIGS. 2 and 3, fuel injector 310 may be a dual fuel injector allowing for operation on gas fuels or liquid fuels. When operating on a gas fuel, the gas fuel is supplied to the gas fuel passage 322 via gas fuel fitting 317. The gas fuel is directed into gas gallery 327 where the gas fuel is directed into and through gas fuel annulus 335. The gas fuel exits gas fuel annulus 335, is mixed with compressor discharge air passing through air cavity 338 and outlet swirler 355, and is combusted in the combustion chamber 305.

When operating on a liquid fuel, the liquid fuel is supplied to the liquid fuel passage 321 via liquid fuel fitting 316. The liquid fuel is directed through liquid fuel inlet 344 and into liquid gallery 337 where the liquid fuel is directed into and through liquid fuel annulus 336. The liquid fuel may be swirled or redirected circumferentially within liquid fuel annulus 336 prior to exiting liquid fuel annulus 336. During liquid fuel operation, air may be directed through gas fuel passage 322, gas gallery 327, and gas fuel annulus 335, which may be mixed with the liquid fuel as the air exits gas fuel annulus 335. The fuel air mixture is combusted in the combustion chamber 305.

Liquid fuel passage 321 and gas fuel passage 322 may be non-symmetrically located within stem 320 rather than being coaxial with stem 320. During operation of gas turbine engine 100, stem 320 may be significantly hotter than either the liquid fuel or gas fuel being used in the combustion process. Heat transfer from stem 320 to the fuel may result in temperature gradients in stem 320 around liquid fuel passage 321 or gas fuel passage 322. These temperature gradients within stem 320 may result in a deflection of fuel injector 310. A deflection in fuel injector 310 may result in high stresses in the mated parts between fuel injector 310 and combustion chamber 305, such as outlet swirler 355 and grommet 306.

Liquid heat shield 360 and liquid heat shield gap 369 may prevent or reduce the heat transfer between the stem 320 and the liquid fuel within the liquid heat shield 360. Gas heat shield 380 and gas heat shield gap 389 may prevent or reduce the heat transfer between the stem 320 and the gas fuel within the gas heat shield 380. This prevention or reduction in heat transfer may prevent or reduce the formation of temperature gradients, the deflection of fuel injector 310, and the stress between mated parts. Further, the prevention or reduction in heat transfer between stem 320 and the liquid fuel may prevent the liquid fuel from pyrolyzing (often referred to as liquid fuel coking).

The preceding detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. The described embodiments are not limited to use in conjunction with a particular type of gas turbine engine. Hence, although the present disclosure, for convenience of explanation, depicts and describes a particular fuel injector, it will be appreciated that the fuel injector in accordance with this disclosure can be implemented in various other configurations, can be used with various other types of gas turbine engines, and can be used in other types of machines. Furthermore, there is no intention to be bound by any theory presented in the preceding background or detailed description. It is also understood that the illustrations may include exaggerated dimensions to better illustrate the referenced items shown, and are not consider limiting unless expressly stated as such. 

What is claimed is:
 1. A fuel injector for a combustor of a gas turbine engine, the fuel injector comprising: a flange including mounting holes; a fitting boss protruding from the flange; a stem extending from the flange in a direction opposite the fitting boss; a gallery portion at an end of the stem distal to the flange; a gas fuel passage extending from the fitting boss to the gallery portion through the stem; a gas fuel fitting joined to the fitting boss at the gas fuel passage; a gas heat shield in fluid communication with the gas fuel fitting and extending from the gas fuel fitting at least partially through the gas fuel passage, the gas heat shield being sized to form a gas heat shield gap between the gas heat shield and the stem in the gas fuel passage, the gas heat shield gap; and a barrel assembly joined to the gallery portion, the barrel assembly being in fluid communication with the gas heat shield.
 2. The fuel injector of claim 1, wherein the gas fuel passage has a horizontal cylindrical segment shape and the gas heat shield has a hollow horizontal cylindrical segment shape.
 3. The fuel injector of claim 1, wherein the gas heat shield gap is from 5 mils to 15 mils.
 4. The fuel injector of claim 1, wherein the gas heat shield gap is not in fluid communication with the gas heat shield.
 5. The fuel injector of claim 1, wherein the gas heat shield is metallurgically bonded to the gas fuel fitting.
 6. The fuel injector of claim 1, wherein the gas heat shield is from 65 to 85 percent of a length of the gas fuel passage.
 7. The fuel injector of claim 1, wherein the gas heat shield is from 70 to 80 percent of a length of the gas fuel passage.
 8. A fuel injector for a combustor of a gas turbine engine, the fuel injector comprising: a flange including mounting holes; a fitting boss protruding from the flange; a stem extending from the flange in a direction opposite the fitting boss; a gallery portion at an end of the stem distal to the flange; a liquid fuel passage extending from the fitting boss to the gallery portion through the stem; a cap joined to the fitting boss at the liquid fuel passage; a liquid heat shield extending from the cap towards the gallery portion within the liquid fuel passage, the liquid heat shield being sized to form a liquid heat shield gap between the liquid heat shield and the stem at the liquid fuel passage; and a barrel assembly joined to the gallery portion, the barrel assembly being in fluid communication with the liquid heat shield.
 9. The fuel injector of claim 8, wherein the liquid fuel passage has a right circular cylinder shape and the liquid heat shield has a hollow cylinder shape.
 10. The fuel injector of claim 8, wherein the liquid heat shield gap is from 5 mils to 15 mils.
 11. The fuel injector of claim 8, wherein the liquid heat shield gap is not in fluid communication with the liquid heat shield.
 12. The fuel injector of claim 8, wherein the liquid heat shield is metallurgically bonded to the cap.
 13. The fuel injector of claim 12, wherein the liquid heat shield extends to the gallery portion.
 14. The fuel injector of claim 8, further comprising: a gas fuel passage extending from the fitting boss to the gallery portion through the stem; a gas fuel fitting joined to the fitting boss at the gas fuel passage; and a gas heat shield extending from the gas fuel fitting at least partially through the gas fuel passage, the gas heat shield being sized to form a gas heat shield gap between the gas heat shield and the stem at the gas fuel passage.
 15. A dual fuel injector for a combustor of a gas turbine engine, the dual fuel injector comprising: a flange including mounting holes; a fitting boss protruding from the flange; a stem extending from the flange in a direction opposite the fitting boss; a gallery portion at an end of the stem distal to the flange, the gallery portion including a first hollow cylinder shape; a liquid fuel passage extending from the fitting boss to the gallery portion through the stem; a gas fuel passage extending from the fitting boss to the gallery portion through the stem, wherein at least one of the liquid fuel passage and the gas fuel passage is non-symmetrically located within the stem; a cap joined to the fitting boss at the liquid fuel passage; a gas fuel fitting joined to the fitting boss at the gas fuel passage; a liquid heat shield extending within the liquid fuel passage, the liquid heat shield including a first liquid heat shield end joined to the cap and a second liquid heat shield end adjacent the gallery portion; a gas heat shield extending within the gas fuel passage, the gas heat shield including a first gas heat shield end joined to the gas fuel fitting and a second gas heat shield end distal to the gas fuel fitting; and a barrel assembly joined to the gallery portion.
 16. The dual fuel injector of claim 15, wherein the liquid heat shield is sized to form a liquid heat shield gap from 5 to 15 mils between the liquid heat shield and the stem at the liquid fuel passage, and the gas heat shield is sized to form a gas heat shield gap from 5 to 15 mils between the gas heat shield and the stem at the gas fuel passage.
 17. The dual fuel injector of claim 15, wherein the gas heat shield is metallurgically bonded to the gas fuel fitting.
 18. The dual fuel injector of claim 15, wherein the liquid heat shield is metallurgically bonded to the cap.
 19. The dual fuel injector of claim 15, wherein the gas heat shield is from 65 to 85 percent of a length of the gas fuel passage.
 20. The dual fuel injector of claim 15, wherein the gas fuel passage has a horizontal cylindrical segment shape and the gas heat shield has a hollow horizontal cylindrical segment shape. 